L 98-59 b

L 98-59 b is an exoplanet having a size between that of the Earth and Mars and a mass only half that of Venus.[2] It orbits L 98-59, a red dwarf 35 light-years away in the constellation Volans. There are at least 3 (possibly 4) other planets in the system: L 98-59 c, d, e, and the unconfirmed L 98-59 f.[2] Its discovery was announced on 27 June 2019 on the NASA website. It was the smallest planet discovered by TESS[4] until the discovery of LHS 1678b,[5] and was the lowest-mass planet whose mass has been measured using radial velocities[2] until Proxima Centauri d was found in 2022.[6]

L 98-59 b
Artist's impression
Discovery
Discovery date2018[1]
Transit[1]
Orbital characteristics
0.0227 AU[1]
Eccentricity0.09[1]
2.2532 d[1]
StarL 98-59
Physical characteristics
Mean radius
0.85 REarth[2]
Mass0.40 MEarth[2]
Temperature603 K (330°C)[3]

    Characteristics

    L 98-59 b orbits in 2.25 days and stays so close to the star that it receives 22 times more energy than Earth receives from the Sun. There are 4 confirmed planets in the system but they are not in the habitable zone of the host star.[4] The temperature of the planet detected by TESS is 330 °C.[3] In 2022, transmission spectroscopy has indicated that the planet has either no atmosphere or opaque atmosphere with the high-altitude hazes.[7]

    References
    1. "The Extrasolar Planet Encyclopaedia-L 98-59 b".
    2. Demangeon, Oliver D. S.; Zapatero Osorio, M. R.; Alibert, Y.; Barros, S. C. C.; Adibekyan, V.; Tabernero, H. M.; et al. (July 2021). "A warm terrestrial planet with half the mass of Venus transiting a nearby star" (PDF). Astronomy & Astrophysics: 38. arXiv:2108.03323. doi:10.1051/0004-6361/202140728.
    3. "Canicule ? Il fait 330 degrés sur la petite exoplanète découverte par le télescope spatial TESS". Numerama (in French). 2019-07-01. Retrieved 2019-07-30.
    4. Garner, Rob (2019-06-24). "NASA's TESS Mission Finds Its Smallest Planet Yet". NASA. Retrieved 2019-06-29.
    5. Silverstein, Michele L.; Schlieder, Joshua E.; Barclay, Thomas; Hord, Benjamin J.; Jao, Wei-Chun; Vrijmoet, Eliot Halley; Henry, Todd J.; Cloutier, Ryan; Kostov, Veselin B.; Kruse, Ethan; Winters, Jennifer G.; Irwin, Jonathan M.; Kane, Stephen R.; Stassun, Keivan G.; Huang, Chelsea (2022-04-01). "The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc". The Astronomical Journal. 163 (4): 151. doi:10.3847/1538-3881/ac32e3. ISSN 0004-6256.
    6. Faria, J. P.; Suárez Mascareño, A.; et al. (January 4, 2022). "A candidate short-period sub-Earth orbiting Proxima Centauri" (PDF). Astronomy & Astrophysics. European Southern Observatory. 658: 17. arXiv:2202.05188. Bibcode:2022A&A...658A.115F. doi:10.1051/0004-6361/202142337.
    7. A transmission spectrum of the sub-Earth planet L98-59 b in 1.1 – 1.7 µm, 2022, arXiv:2210.10008
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